Long-term Failure Rate of Brackets Bonded with Plasma and High-intensity Light-emitting Diode Curing Lights

Shear strength of metal brackets using LED lamps with different wavelengths: An in vitro comparative study

AIM

To evaluate the shear strength of Orthocem and BracePaste polymerizable cement light-cured with light-emitting diode (LED) units with different wavelengths (Bluephase N) with their high power, low power, and soft start programs in the bonding of metal brackets.

MATERIALS AND METHODS

In vitro experimental research was performed. Mini Roth 0.022 metal brackets (Roth Orthometric brackets) were used. The adhesives were placed on the metal brackets with Orthocem and BracePaste resin cement. To compare the average strengths, the analysis of variance (ANOVA) test was used (P < 0.05).

RESULTS

The average shear strength was better with Bracepaste polymerizable cement compared to Orthocem cement in all its high power, low power, and soft star programs; the highest was Bracepaste with soft start of 26.52 MPa, and the lowest was Orthocem with soft start of 13.92 MPa. When evaluating the differences, it was found that these were statistically significant in all groups (P < 0.05).

CONCLUSIONS

Differences were found in the shear strength of light-curing Orthocem and Bracepaste light-curing cement cured with LED units with different wavelengths in bonding metal brackets to the tooth in vitro.

Failure rates among metal brackets cured with two high-intensity LED light-curing lamps: an in vivo study

OBJECTIVE

The objective of this split-mouth clinical trial was to compare bonding failure rates of metal brackets bonded with two different light-emitting diode (LED) light-curing lamps with different high-intensity power outputs.

MATERIALS AND METHODS

Forty patients were included for a total of 800 brackets that were randomly bonded (left and right sides in a 1:1 ratio) in maxillary and mandibular arches using two different LED devices. An LED of 3200 mW/cm2 and an LED of 5000 mW/cm2 were used in this split-mouth clinical trial. Bonding failures during the initial 6 months of orthodontic treatment were recorded as maxillary versus mandibular, anterior teeth versus posterior teeth, and left side versus right side.

RESULTS

Five dropouts were recorded for discontinuing orthodontic treatment and 700 brackets were analysed in total. The bonding failure rates for 3200 and 5000 mW/cm2 LEDs were 6.0 and 7.4 per cent, respectively (P = 0.450), which were not statistically significantly different. There were no significant differences in bracket survival rates between the LEDs used (P = 0.866). The posterior teeth presented a higher index of bond failures (odds ratio, 3.14; 95% confidence interval, 1.68-5.87; P < 0.001).

LIMITATIONS

Direct comparison was only done between two high-intensity LED lights rather than against conventionally used halogen lights.

CONCLUSION

Similar bonding failures were recorded using both LED devices (3200 and 5000 mW/cm2). Significantly more bonding failures occurred in premolar teeth than in anterior teeth.

Effect of different bonding protocols on degree of monomer conversion and bond strength between orthodontic brackets and enamel

The objective of the present study was to evaluate the effect of different surface treatments and polymerization protocols on the bond strength of brackets to enamel, and the degree of conversion of the bonding agents. 120 bovine crowns were embedded in acrylic resin blocks and sanded. Next, the blocks were randomly assigned into 12 groups. Metal brackets were bonded to enamel according to the "surface treatment" factor (A: Phosphoric Acid; ATxt: Phosphoric Acid + Transbond XT Primer®; Tse: Transbond Plus Self Etching Primer®; and SBU: Scotchbond Universal®) and "polymerization" factor (R20: Radii-Cal®/20 seconds; V20: Valo Cordless®/20 seconds; and V3: Valo Cordless®/3 seconds). All samples were stored for 6 months (water, 37ºC) and then subjected to a shear bond strength test (SBS). Bond failures were classified according to the Adhesive Remnant Index (ARI) and analyzed with the Kruskal-Wallis and Mann-Whitney tests (5%). Using the same factors, 120 resin discs were made to assess the degree of conversion (DC) of the monomer. Data from the SBS (MPa) and DC (%) were analyzed by analysis of variance (2 factors) and Tukey's test (5%). For the SBS, the factors "polymerization" (R20 = 8.1B; V20 = 13.2A; V3 = 5.2C, p = 0.0001) and "surface treatment" (A = 3.1C; ATxt = 13.6A; Tse = 12.3A; SBU = 6.3B, p = 0.0001) were statistically significant among groups. The highest adhesion value were found for the ATxt/V20 group (22.2A) and the lowest value for the A/R20 group (1.2E). Regarding ARI, score 2 was the most prevalent in groups A, ATxt, V20 and V3, while score 4 was the most prevalent in the Tse, SBU and R20 groups, with no significant difference between them (p = 1.0). Regarding DC, the factors "polymerization" (R20 = 66.6A; V20 = 58.4B; V3 = 45.1C, p = 0.0001) and "surface treatment" (A = 52B, ATxt = 59.7A, Tse = 51.4B, SBU = 63.8A, p = 0.0001) were statistically significant. Tse was more sensitive to the variations in polymerization protocols than the other surface treatments. Treatment A did not present suitable bond strength or degree of conversion.

Clinical effect of reducing curing times with high-intensity LED lights

OBJECTIVE

To evaluate the clinical performance of brackets cured with a high-intensity, light-emitting diode (LED) with a shorter curing time.

MATERIALS AND METHODS

Thirty-four patients and a total of 680 brackets were examined using a randomized split-mouth design. The maxillary right and mandibular left quadrants were cured for 6 seconds with a high-intensity LED light (3200 mW/cm(2)) and the maxillary left and mandibular right quadrants were cured for 20 seconds with a standard-intensity LED light (1200 mW/cm(2)). Alternating patients had the quadrants inverted for the curing protocol. The number and date of each first-time bracket failure was recorded from 199 to 585 days posttreatment.

RESULTS

The bracket failure rate was 1.18% for both curing methods. The proportion of bracket failure was not significantly different between curing methods (P  =  1.000), genders (P  =  1.000), jaws (P  =  .725), sides (P  =  .725), or quadrants (P  =  .547). Posterior teeth exhibited a greater proportion of failures (2.21%) relative to anterior teeth (0.49%), although the difference was not statistically significant (P  =  .065).

CONCLUSIONS

No difference was found in bond failure rates between the two curing methods. Both methods showed bond failure rates low enough to be considered clinically sufficient. The high-intensity LED light used with a shorter curing time may be considered an advantage due to the reduced chair time.

Long-term evaluation of clinical performance of direct-bonded brackets: an epidemiologic survey

AIM

The objective of the current epidemiologic study was to investigate characteristics associated with bracket failure in bonded brackets.

MATERIALS AND METHODS

A retrospective study on data of 144 patients treated during 2009 to 2012 was done. Baseline data including age, gender, malocclusion, bite type and debonding incidences per teeth were retrieved. ANOVA analysis and t-test were used to evaluate the data.

RESULTS

Second premolar teeth had significantly higher debonding incidences. Patients' age was negatively correlated with debonding incidences. No difference was observed for various types of malocclusion (class I, II and III), arch side (right or left) or arch location (upper or lower). However, deep bite patients had significantly higher failure incidents.

CONCLUSION

For a total of 144 patients with 2,524 bonded brackets, the overall failure rate was 7.8%. Deep bite was the only factor that was associated with higher bracket failure. The bracket failure incidents tend to decrease as patients age increase.

CLINICAL SIGNIFICANCE

Deep bite patients and also second premolar teeth seem to be especially prone to debonding incidents. Care must be taken to avoid premature contacts in deep bite patients. Also strict adherence to moisture control protocols when bonding second premolar teeth is recommended since these teeth are at increased risk for debonding.

Split-mouth designs in orthodontics: an overview with applications to orthodontic clinical trials

Split-mouth designs first appeared in dental clinical trials in the late sixties. The main advantage of this study design is its efficiency in terms of sample size as the patients act as their own controls. Cited disadvantages relate to carry-across effects, contamination or spilling of the effects of one intervention to another, period effects if the interventions are delivered at different time periods, difficulty in finding similar comparison sites within patients and the requirement for more complex data analysis. Although some additional thought is required when utilizing a split-mouth design, the efficiency of this design is attractive, particularly in orthodontic clinical studies where carry-across, period effects and dissimilarity between intervention sites does not pose a problem. Selection of the appropriate research design, intervention protocol and statistical method accounting for both the reduced variability and potential clustering effects within patients should be considered for the trial results to be valid.